JPH01229259A - Photosensitive body - Google Patents

Abstract

PURPOSE:To obtain stable printing having sufficiently sharp display at edges without being influenced by the fluctuation of output energy of a light source by laminating a switching layer consisting of a material which causes sudden change of electric resistance when an impressed voltage exceeds a threshold voltage, on a photoconductive layer on an electroconductive base body. CONSTITUTION:Light carriers are generated on a irradiated part alone of a photoconductive layer 3 when a photosensitive body 1 is charged uniformly and irradiated with a light pattern. Negative carriers are drifted to a switching layer side 4 and the positive carriers are drifted to an electroconductive base body side 2. In this case, when an electric voltage applied to the switching layer 4 having high resistance is increased gradually and exceeds a threshold value of the layer 4, the resistance of the layer 4 decreases suddenly to a low resistance, then an electrostatic latent image is formed by neutralizing a surface potential of the photosensitive body 1. Thus, a stable distribution of surface potential of the photosensitive body is obtd. without being influenced by the fluctuation of exposing energy, and a stable printing having sharp display of edges is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photoreceptor used in electrophotographic recording devices such as copying machines, facsimiles, and optical printers.

[Prior art] Conventional photoreceptors include a-3i, 5e-Te, and OP.
There are many types such as C, and their structure is carrier generation layer (C'GL) due to the requirements for charging ability and spectral sensitivity.
There is also a functionally separated type consisting of a carrier transport layer (CTL) and a carrier transport layer (CTL).

[Problem to be solved] The relationship between exposure energy and surface potential of these conventional photoreceptors is as shown in FIG. 6, where the vertical axis is the photoreceptor surface potential V and the horizontal axis is the exposure energy P. The sensitivity characteristics of the photoreceptor are expressed by a slightly concave curve a. When an electrostatic latent image is formed on a photoreceptor having such sensitivity characteristics, variations in the light emission energy of the light source will cause variations in the surface potential of the exposed portion. If a laser is used as a light source to suppress this variation, the temperature of the laser must be controlled to suppress temperature fluctuations in the output, and the lens must be adjusted to keep the energy constant at the center and periphery of the scan. The design becomes complicated. When using an LED array,
Chip selection and output correction must be performed based on the emission energy of the LED chips.

In addition, the intensity distribution of the light beam is as shown in the curved line in Figure 7, and the center of the dot has high exposure energy, but the peripheral area has low exposure energy. The Omagari potential distribution looks like curve C,
Either a sufficient surface potential is obtained at the center of the dot, or the potential is gradually lowered at the periphery, which is one of the factors that worsens the edge cutting of the toner image.

Therefore, the present invention has the advantage that even if the exposure energy of the light source fluctuates, the surface potential of the photoreceptor at the light irradiation part remains constant, and as a result, it is not affected by the output energy of the light source and has a stable edge with good sharpness. The object of the present invention is to provide a photoreceptor that can print with high quality.

[Means for Solving the Problems] In order to achieve the above object, in the photoreceptor of the present invention, a photoconductive material made of a substance that generates an amount of carriers that increases in accordance with an increase in the amount of light received is provided on the upper surface of the conductive substrate. A switching layer made of a material that rapidly transitions from a high resistance state to a low resistance state when an applied voltage exceeds a threshold value is stacked.

The switching layer is laminated on the outside of the photoconductive layer, and in this case, light is irradiated from the switching layer side.

In addition, -1- the electrically conductive substrate is formed of a transparent shell, and 1.

a photoconductive switching layer is laminated inside the photoconductive layer,
In this case, light is irradiated from the conductive substrate side.

[Example] An embodiment of the present invention will be described with reference to the drawings.

The photoreceptor 1 shown in FIG. 1 is drum-shaped, and has an OPC photoconductive layer 3 formed on the upper surface of a drum-shaped conductive substrate 2 made of aluminum, and a switching layer 4 formed on the upper surface. It is made up of three layers. In this example, an organic photosensitive material such as titanyl phthalocyanine is used as the material forming the photoconductive layer 3, and Cu-TCNQ (7,7,8,8-
Tetracyanoquinodimethane) is used.

FIG. 2 shows the switching characteristic d of this Cu-TCNQ, with the vertical axis representing the current I and the horizontal axis representing the applied voltage V.

That is, this switching layer 4 has V = V +,
Until then, it shows an ohmic high resistance state. ■ From V T
Up to l+ (threshold voltage), it exhibits characteristics that deviate from the ohmitter, and at V=VTll, abrupt switching from a high resistance state to a low resistance state occurs. This low resistance state is maintained while a voltage equal to or higher than VTII is applied. When the voltage is turned off, it quickly returns to the high resistance state. In addition, the resistivity P H, P and threshold voltage VTH at high resistance and low resistance of Cu-TCNQ are as follows:
Each PH ~ 10 Ω・mark.

P ~10Ω・Cm, v ~103■/cI
Tl de L
THru. In addition, good switching I (P/PL~10) is achieved.

Next, the principle of operation of the present invention will be explained with reference to FIG. First, the photoreceptor 1 is uniformly charged by corona charging or the like as shown in area Sl. After charging, when a light pattern is irradiated from the switching layer 4 side, optical carriers are generated only in the light irradiated area, as shown in region S2. Due to the electric field applied to the photoreceptor 1, negative carriers drift toward the switching layer 4 side, and positive carriers drift toward the conductive substrate 2 side. Since the switching layer 4 is in a high resistance state at this time, carriers are accumulated at the interface. As a result, the voltage of the electric field applied to the switching layer 4 increases, but if the exposure energy P is small, that is, the number of generated carriers is small, this voltage does not reach the threshold voltage vTll, and the photoreceptor surface charge is not neutralized. . However, as in region S3, the exposure energy P is vTll
(At this time, when the voltage of the electric field applied to the switching layer 4 by the generated carriers is vTll), the J switching layer 4 suddenly becomes a low resistance state, and the carriers accumulated at the interface pass through the switching layer 4, and the photoreceptor surface The streetcar G7 is neutralized and an electrostatic latent image is formed.

That is, if the photoreceptor 1 of the present invention is used, the photoreceptor sensitivity characteristic with a threshold value at PTH will be obtained as shown in line e in FIG. 4, where the vertical axis is the photoreceptor surface potential V and the horizontal axis is the exposure energy P. is obtained.

Furthermore, Fig. 5 shows the potential distribution on the surface of the photoreceptor.
The intensity distribution of the light beam is similar to the curve shown in FIG.
The center of the dot has high exposure energy and the periphery has low exposure energy, but the photoreceptor surface potential distribution generated by this light beam is as shown by line f, and even in the periphery of the dot, the center has low exposure energy. A sufficient surface potential similar to that obtained is obtained, resulting in a rectangular line. This results in stable printing with good edges of the toner image.

Note that the switching layer is not limited to the upper Cu-TCNQ, but also C-TNAP (11, 11, 1
A material having switching properties such as 2,12-tetracyano-2°6-naptoquinodimethane) or a chalcogenide-based amorphous semiconductor (eg, Te-As-Ge-8i) may be used.

Further, the photoreceptor is not limited to the drum shape as shown in the first figure, but may be configured in the form of a flat plate. Alternatively, the conductive substrate may be formed of a transparent material, the switching layer may be laminated inside the photoconductive layer, and light may be irradiated from the side of the conductive substrate.

[Effects] Since the present invention is configured as described above, a stable photoreceptor surface potential distribution at the light irradiation part can be obtained without being affected by fluctuations in exposure energy on the surface of the photoreceptor, As a result, in the case of a laser light source, temperature control of the laser becomes unnecessary, and lens design becomes easier. Also LE
In the case of the D light source, the yield of heads improves and output correction becomes unnecessary. In addition, stable printing with sharp edges is possible.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a switching characteristic diagram of a switching layer, Fig. 3 is a diagram explaining the principle, Fig. 4 is a sensitivity characteristic diagram of a photoconductor, and Fig. 5 is a photoconductor sensitivity characteristic diagram. The surface potential distribution diagram of the body, Figure 6 is the sensitivity characteristic diagram of the conventional photoreceptor, and Figure 7 is the sensitivity characteristic diagram of the conventional photoreceptor.
The figure is a surface potential distribution diagram of a conventional photoreceptor. DESCRIPTION OF SYMBOLS 1... Photoreceptor, 2... Conductive base, 3... Photoconductive layer, 4... Switching layer. 1-1 9- 茫to

Claims (6)

[Claims] (1) On the top surface of the conductive substrate, there is a photoconductive layer made of a substance that generates an amount of carriers that increases as the amount of light received increases, and when the applied voltage exceeds a threshold value, the resistance changes rapidly from a high resistance state to a low resistance state. 1. A photoreceptor comprising a switching layer made of a substance that transitions to . (2) The photoreceptor according to claim 1, wherein the switching layer is laminated on the outside of the photoconductive layer, and light is irradiated from the switching layer side. (3) The conductive substrate is made of a transparent material, the switching layer is laminated inside the photoconductive layer, and light is irradiated from the conductive substrate side. Item 1. Photoreceptor according to item 1. (4) The switching layer is Cu-TCNQ (7, 7,
8,8-tetracyanoquinodimethane). The photoreceptor according to any one of claims 1 to 3. (5) The above switching layer is C-TCNQ (11, 11
, 12,12-tetracyano-2,6-naptoquinodimethane). (6) The photoreceptor according to any one of claims 1 to 3, wherein the switching layer is made of a chalcogenide-based amorphous semiconductor.